Sorry to disagree with you jonwilly (an interesting title in Thailand, n'est pas?)
Fortress Singapore was the title of the British Garrison and British Military Government on the Island (a bit like 'Troops Aldergrove' in Belfast). It was not concocted by a journalist.
I concur that 'Singapore Burning' by Colin Smith is an excellent and sympathetic read; his other book on Vichy France (England's Last War with France) is equally good.
A few years ago I was awarded a Defence Fellowship and studied intelligence aspects of the Malay Peninsular and Singapore. In c 1938 the JIC sent Wg Cdr Wigglesworth to Singapore to conduct a review of the intelligence organisation. After reviewing Combined Intelligence Bureau Malaya (CIBM) Wigglesworth noted:
Here [Singapore], CIBM Officers from all three Services and MI5 pooled and exchanged intelligence across South East Asia. Cooperation was uncommonly good, but sources poor.
He also noted that most material on the Japanese to the Far East Combined Bureau (MI5/SIS regional office) was based on radio intercepts, implying that HUMINT sources were few.
Pre-war Special branch ran particularly effective operations against the Chinese Communists and Japanese agents. From 1931 until 1946, the Sec Gen of the ‘Nanyang’ (Overseas) CHICOM party was a British ‘asset’. However, the Japanese espionage was extremely well organised, better resourced and more than a match for the British.
Post War Lt Gen Perceval played down many of the failings. Colin Smith is more objective. The Japanese were at the end of their supply chain and British denial methods (Jahore causeway, airfield denial) weren’t particularly efficient. The use of gas in a defensive role was even considered. Aircraft were definitely drawn from the 2nd XV (Wirraways, Buffalos, Vildebeests, a handful of Blenheims, for example) and some British troops were poorly trained and some exhibited poor discipline (eg the Australian contingent). Nonetheless the Japanese didn’t get away lightly. They did sustain very high casualty rates (the numbers are not known) and they suffered a fair number of Naval and air losses as well. But in the East, life is cheap.